Self-venting double wall receptacle



Jan. 21, 1964 F. CORNELIUS 3,118,560

SELF-VENTING DOUBLE WALL RECEPTACLE Filed Oct. 16, 1961 WW/M' 7 M United States Patent SELF-VENTING DOUBLE WALL RECEPTACLE Nelson F. Cornelius, Coon Rapids, Minn; Ivadeli A.

Cornelius, executrix of the estate of said Nelson F.

Cornelius, deceased, assignor to N.F.C. Engineering Company, Anoka, M'mn.

Filed Get. 16, 1% Ser. No. 145,173 7 Claims. (Cl. 220-14) This invention relates to self-venting double wall structures and the method of venting such structures and more particularly to double wall containers constructed of plastic material and the method of venting these plastic type double wall containers.

One of the problems associated with the use of double wall type plastic containers such as tumblers, serving dishes and the like is the tendency for these double wall plastic containers or receptacles to fail by deformation and separation of the walls when these containers are subjected to elevated temperatures. Generally speaking, these containers are constructed of inner and outer plastic shells or walls formed of thermoplastic and joined together with a sealed eifect to define an insulating chamber therebetween. In some of these structures an insulating insert can be interposed between the respective inner and outer walls to occupy a part or substantially all of the insulating chamber defined between the respective walls. However, there is always a predetermined quantity of gas contained within the insulating chamber, the gas generally being air confined within the chamber at atmospheric pressure.

It will be seen that when the receptacle or container of this type is subjected to elevated temperatures such as by placing heated food within the container or submerging the container into heated waters as in dish washers, the confined gas will tend to expand and thereby result in an increase in the fluid pressure exerted by the gas on the walls of the container. This increase in pressure resulting from elevating the temperature of the confined gas will be in accordance with the laws of Boyle and Charles. it will be appreciated that when the ambient temperature is sufficient to lower the strength of the plastic the pressure buildup within the chamber will distort the plastic shells.

Since it is essential to maintain the insulating chamber between the walls in sealed condition, the prior art devices have no provision for venting of the double wall type structures to permit a reduction of the gas pressure in response to an increase in the temperature of the container.

It has, therefore, been necessary to construct these double wall plastic receptacles from the high grade thermoplastic since lower grade plastic has a lower distortion heat temperature. The distortion heat temperature of a plastic is tnat point at which the plastic will deform when subjected to increased temperature. It will, therefore, be seen that as the temperature increases and the plastic tends to soften and deform, the exertion of pressure by the expanding gases will tend to permanently deform the walls of the container.

It is an object of this invention to provide a highly efiicient spaced double wall plastic structure, of simple and inexpensive construction, the walls of the structure being made from a thermo heat resistant plastic having an insulating chamber therebetween, and having means for automatically venting the insulating chamber in response to changes in gas pressure within the insulating chamber to thereby prevent deformation of the double wall plastic structure when subjected to elevated temperatures.

Another object of this invention is the provision of a novel and improved automatic selfventing, double wall, heat-insulated receptacle or container wherein two pre- Edidfihd Patented Jan. 21, 1964 molded plastic shells are joined with sealed effects defining an insulating chamber therebetween, the shells having a valve means operative in response to changes in gas ressure within the insulating chamber for automatically venting the insulating chamber whereby the tendency of the shells to deform at elevated temperatures is greatly minimized to thereby make possible the construction of these containers of low grade low heat resistant plastic material.

Another object of this invention is the provision of a novel and improved heat insulated double wall container of the class described having automatic self venting means and including a pair of plastic shells joined with sealed effect along interengaging edges by means of a friction fit thus obviating the need of a cementing material so that the respective shells of the container need not be formed of compatible plastics thereby allowing the containers to be manufactured of wide varieties of heat resistant type plastics including both the high grade expensive plastics as well as the cheaper grade plastics.

A more specific object of this invention is the provision of a novel double wall, heat insulated receptacle or container comprised of a pair of concentrically arranged shells each formed of a heat resistant plastic and joined with a sealed effect to define insulating chamber therebetween, opposed wall portions of the shells cooperating with each other to define a normally closed diaphragm valve interconnecting the insulating chamber in response to changes in gas pressure within the chamber when the receptacle is subjected to elevated temperatures.

A still further object of this invention is the provision of a novel method of venting a heat insulated double wall container constructed of concentrically joined plastic shells wherein the relative movement of the shells actuates a valve for automatically venting the insulating chamber between the shells upon changes of gas pressure within the chamber and thereafter closing the valve upon reduction of gas pressure within the chamber.

These and other objects and advantages of my invention will more fully appear from the following description made in connection with the accompanying drawings wherein like character references refer to the same or similar parts throughout the various views, and in which:

FIG. 1 is a side view taken partly in section and partly in elevation of a lid cover insulated serving dish adapted to hold hot or cold food, ice, beverages and the like, showing the respective outer and inner shell members of the body and lid joined together with sealed effect and illustrating details of construction of the self-venting structure; and

FIG. 2 is a view partly in side elevation and partly diametrical vertical section showing another embodiment of my invention in the form of an insulated tumbler which utilizes inner and outer shells joined together with sealed effect and which also includes the novel self-venting diaphragm valve construction.

While only two embodiments of insulated plastic receptacles or vessels constructed in accordance with our invention are illustrated, it will, of course, be understood that a large variety of different receptacles, containers and food and beverage servers of novel construction may all be produced commercially in accordance with my invention.

Referring now to the lid-covered insulated serving dish container illustrated in FIG. 1, it is pointed out that the body of the container is comprised of inner and outer shells indicated in their entireties by the numerals 6 and 7 respectively and which are molded preferably from heat-resisting grades of plastic. The inner and outer shells are hard and substantially rigid after the molding process and the outer shell may be molded from a thermoplastic material such as, for example, a copolymer of a polystyrene and acrylonitrile which may be transparent or opaque. The inner shell in the preferred embodiment is preferably formed of molded opaque polypropylene which has somewhat resilient qualities. However, both the inner and outer shells may also be constructed from thermo-plastic by molding the shells by compression from suitable thermo setting material such as melamine phenolics, etc.

The outer shell 7 includes a substantially flat bottom wall portion 8 having peripheral wall portions 9 integrally formed therewith and extending upwardly therefrom. The inner surface of the transparent outer shell is preferably coated with a thin layer of reflective coating preferably metallic such as bronzing lacquer or metal applied by utilization of a vacuum metallizing process or by application and adherence of a thin metallic foil to form such a coating identified as 1% in FIG. 1. This coating of reflective material such as thin metal foil or metallic spray not only increases the insulating efiiciency of the double wall structure but also imparts a highly ornamental appearance to the receptacle.

t will be noted that the bottom wall 8 of the outer shell'7 is provided with a plurality of small arcuate concave legs 11 which project downwardly somewhat from the general plane of the bottom wall portion 8 so that the latter will be supported in spaced relation upon a supporting surface. The bottom wall 8 is provided with a tubular outlet 12 having a bore or orifice 12a therein,

. the lower portion of which is tapered downwardly to deline a valve seat 13. The upper marginal edge of the outer shell 7 is enlarged as at 14 and actually comprises a male member of a socket connection between the inner and outer shell of the body of the container.

It w ll be seen that the inner shell 6 also includes a substantially flat bottom wall portion 15 and peripheral walls 16 integrally formed therewith and extending upwardly therefrom. The upper edge portion of peripheral walls of the inner shell 6 is provided with a depending flange 17, the latter terminating downwardly in an annular downwardly facing groove or socket 13 which comprises the female .part of the joint for snugly receiving the male annular element 14 therein. In this connection,

it will be noted that the female annular socket 18 is .rial to join their respective inner and outer shells in sealed relation so that the inner and outer shells may now be constructed of plastics which do not necessarily have to. be compatible with respect to a plastic cement.

The inner shell member s is of the same general configuration as that of the outer shell 7 but is smaller dimensioned so that the shells are joined to define an insulating chamber w therebetween as pointed out above. In the preferred embodiment, the insulating chamber receives an expanded foam type plastic insert 23 therein which is a preformed preferably of styrene foam to have a general configuration corresponding to that of the insulating chamber 19. This insert is constructed to have a small clearance for assembly and linear expansion thereof.

Thus, the insert when positioned within the chamber 19 will fit therein in snug-fitting relation although this insertwill not completely fill the insulating chamber.

The bottom wall 15 of the inner shell 6 is provided with 2. depending valve element 21 integrally formed therewith and depending therefrom. It will be noted that the valve element 21 has a tapered lower end portion 22 which seats against the tapered seat portion 13 of the outlet 12, thus closing the insulating chamber with re- 7 spect to the exterior. It will be noted in the embodiment illustrated in PEG. 1 that the depending valve element 21 is centrally located with respect to the bottom wall 15 of the inner liner or shell 6 and is normally urged against the valve seat 13. In this connection, it is pointed out that the bottom wall 15 of the inner shell 6 will be molded so that the shell is substantially flat and planar while the valve element 21 is of a length and shape to urge the bottom 15 slightly out of its planar configuration when the inner and outer 51-3118 are assembled. With this arrangement, the resiliency of the inner shell 15 constantly normally urges the valve element 21 to its seated position so that the valve element 21 is slightly preloaded when the serving dish is assembled. It will further be noted that the premolded insulating insert 2% is suitably apertured as at 28 to accommodate the tubular outlet 12 and the valve element 21.

From the foregoing it will be noted that the assembled device is similar in some respects to the insulated plastic containers and the process for making the containers described in my co-pending patent application, Serial Number 798,228, now Patent No. 3,094,448. However, since the inner engaging marginal edge portions of the inner and outer shells 6 and 7 respectively are preferably interconnected by a snap coupling resilient fitting, instead of the cement material of the type described in the aforementioned applications, there is no need to vent the assembled containers to permit the escape of solvent vapors resulting from the heating and baking steps therein. It is pointed out, however, that a solvent type cementing material may also be used in regard to the instant invention.

The outer shell 7 of the receptacle, shown in FIG. 1, is provided with a pair of socket members 24 each having a downwardly open socket therein. it will be noted that these socket members 23 are disposed on opposite sides of the outer shell 7 and each receive the upstanding legs 26 of one of a pair of handle members 25. It will be noted that the handle members 25 are each suitably constructed of metal such as plated wire and each of the handles 25 is provided with an upper portion 27 which projects inwardly towards the receptacle and is adapted to be moved into engagement with the depending flange 17 of the inner shell 6. This upper locking portion 27 of the handle 25 actually is cammed over the protruding female socket in a snap-over locking fashion to secure the handles to the body portion of the serving dish.

The insulated serving dish illustrated in FIG. 1 also includes a lid comprising an inner shell 28 and an outer shell member 29 constructed generally in a similar manner to the construction of the respective shell body member. The inner shell 23 includes an upstanding annular shape. The outer shell member 23 of the lid is provided with an annular recess member ill, the recess being suitably shaped and contoured to receive the malecoupling eleient 3-9 in snug fitting relation so that the inner and outer shell may be sealingly secured around this annular seam by a friction fit coupling.

The lid is also provided with a premolded semi rigid expanded plastic foam insert 32 also constructed preferably of styrene foam type plastic as in the manner of the insert 2%. It will be noted that the insert member 32 does 'not completely fill thespace defined by the joined inner and outer shells so that there is provided clearance for expansion of the insert. It will also be noted that the insert 32 is provided with a suitable centrally located aperture 32:: through which projects an upstanding lug 33, the latter being integrally formed with the inner shell member 23. This lug 33 in the preferred embodiment projects upwardly through the outer shell 29, the latter having an appropriate aperture therein and is threadedly engaged by a self threading plated knob 34, the latter having a threaded socket 35 therein. The aperture or slot 36 in the outer shell 29 is of a sufficient size to constitute a permanent vent for the lid.

It will be noted that the insulating chamber 19 contains a predetermined amount of air. In this connection it is pointed out that the molded semi rigid foam insert 20 is of porous construction and includes a plurality of plastic encapsulated air bubbles. Thus, when the serving dish is provided with a heated food or in the event the serving dish is immersed in dish water wherein the temperature of the water there n sometimes approaches boiling, the trapped air or gas within the insulating chamber will expand and exert pressure on the respective inner and outer shells of the body of the container in accordance with the law of Boyles and Charles. The internal pressure is of a sufficient magnitude to cause permanent deformation of the shells especially if the plastics are of the cheaper or low grade heat resistant plastic. Plastics become slightly softened at the elevated temperatures and when the ambient temperature is sufficient to soften the plastic, the shells will be permanently deformed by the expanding gas pressure.

For example, if the inner and outer shells are permanently sealed under atmospheric pressure at 70 F., a considerable positive pressure build up at elevated temperature will be sufiicient to distort the vessel when the ambient temperature is sufficient to lower the strength of the plastic. Using Charles law of pressure and temperature (of a perfect gas), where the volume of the insulating chamber 19 remains relatively constant, the following example may be shown in which T and T are absolute temperatures in degrees Fahrenheit; and

'P and P are pressures and pounds per square inch absolute.

T represents the initial temperature and T the new temperature; while P is the initial pressure and P is the new pressure.

If the vessel is sealed at 70 F., then raised to 212 F., by means of submersion in boiling water as for instance during the washing operation in a dish washer, the following figures would apply when substituted in the above referred to formula.

14.7 X 530 67 2 X=18.638 p.s.i. absolute.

This means that the difference in the pressure of the sealed insulating chamber 19 is raised approximately 4 p.s.i., so there is a distorting force of 4 pounds for each square inch of surface. This force is sufficient enough at most lower cost thermo plastic material to cause permanent distortion thereof at the elevated temperatures.

However, it will be seen that when a predetermined gas pressure has been reached, the bottom wall of the serving dish will function in the manner of a diaphragm type valve and will be moved away from the bottom wall 3 of the outer shell 7. During this spreading movement of the wall portions 8 and 15, it will be noted that the valve element 21 will move out of seated relation with respect to the valve seat 13 and the insulating chamber 19 will be in communicating relation with the exterior. This will relieve the gas pressure since the heated expanded gases will quickly flow through the outlet 12. The inherent resiliency of the bottom wall 15 of the inner shell '6 will immediately cause the valve element 21 to be returned to seated sealed relation with respect to valve seat 13. By adjusting the length of the valve element 21 to give the proper preload, a low pressure differential is obtained at elevated temperatures, so that the difference between internal expanding pressure and the exterior pressure may be reduced to approximately 0.5 p.s.i., or a relatively low distorting force between the inner and outer shells. Thus, it will be seen that the insulating chamber will again be quickly sealed with respect to the exterior.

It will be seen that because of the particular shape of the serving dish body and especially the configuration and relatively large surface area of the bottom wall 15 of the inner shell 6, this inner shell will tend to be moved upwardly in response to increased pressures caused by the expanding gases in the insulated chamber when subjected to elevated temperatures. Since the outer shell is preferably somewhat more rigid than the resilient inner shell 6, the inner shell will react to the increased gas pressures of the insulated chamber and bottom 15 will, therefore, be moved upwardly for unseating the valve element 21 from outlet closing relation with respect to the outlet 12.

Thus, the bottom wall 15 actually functions as a diaphragm-type valve. It will be appreciated that in the event the particular wall portion of the inner shell which is utilized as the diaphragm valve of the receptacle has a smaller surface area than the remaining portions of the inner shell, it would then be necessary to make this wall portion thinner with respect to the remainingportion of the inner shell so'that the selective wall portion would react to pressure. However, the great surface area of the bottom wall 15 obviates the necessity of venting this particular portion of the wall since the bottom 15 of this inner shell would necessarily be the first portion of the inner shell to react to increased gas pressure.

It has been found that the premolded expanded side plastic insert 20, as pointed out above, is comprised of a plurality of foam cells each containing a small volume of gas or air. These cells are subject to minute fractures for the same reasons referred to with respect to the inner and outer shells 6 and 7. Therefore, if some of the cells should break down and some gas is permitted to escape from previous incapsulated effect of the foam, this gas is then permitted to. escape from the vessel automatically at elevated temperatures thus protecting the receptacle and foam from further damage.

After the valve element 21 is moved into seated relation with respect to its valve seat, the valve therefore not only prevents the entrance of air into the insulating chamber but also permits the entrance of moisture when a receptacle is being subjected to washing operation and is submerged in cold water. This self-sealing arrangement of the valve is essential in order to retain the insulating value of the receptacle.

Referring now to FIG. 2, it will be seen that'we have illustrated an insulated double wall self-venting tumbler which also advantageously incorporates the features of my present invention. This tumbler also includes molded inner and outer shells 4t and 41 respectively. These shells are also molded from high heat resistant grades of plastic which when molded are substantially rigid. Again, as in FIG. 1, thermo-plastic material such as, for example, a copolymer or polystyrene and acrylonitrile may be successfully utilized in the construction of the outer shell 41.

This outer shell may also be transparent or opaque in the manner of the serving dish illustrated in FIG. 1. The outer shell includes a base or bottom 42 having a substantially flat central portion and diverging marginal portion 42a. The outer shell 41 also includes upstanding peripheral annular walls 43 integrally formed with the bottom wall portion 42 and sustained upwardly therefrom. The upper marginal portions of the anular peripheral walls 43 are provided with a plurality of annular spaced apart ribs 44, this upper marginal portion being recessed to define an annular shoulder 45. The bottom wall 42 of the outer shell 41 is provided with a centrally located inlet 46 having a slightly tapered bore 46a therein. The upper peripheral portions of the outlet 46 define an annular valve seat 46b to be more fully described hereinbelow.

The inner shell 40 is constructed of similar shape and configuration as that of the outer shell 41 but is preferably constructed of polypropylene and includes a bottom wall 47 and having integrally formed therewith upstanding peripheral walls 48, the latter having a depending annular flange 49 integrally formed therewith. Depending annular flange 49 is provided with a plurality of annular grooves or recesses 50, each adapted to be snapped into friction engagement with one of the annular ribs 44. The lower terminal portion of the depending flange 49 defines an abutting shoulder 51 for cooperating abutting relation with shoulder 45 on the outer shell il. Again, it will be noted that the use of the friction type snap coupling of the inner and outer shell not only permits a sealed etlect to be obtained but also obviates the need of compatible cementing resins for use in securing the inner and outer shells together. Again, it is pointed out that a very important functional advantage with this type of arrangement is that different kinds and grades of plastics may be used without being restricted by the necessity of plastics having compatible cementing resins.

When the inner and outer shells are so assembled, the shells will be disposed in spaced apart relation defining an insulating chamber 52 therebetween. This chamber may, in the preferred embodiment, be partially filled with a premolded and expanded foam styrene plastic reinforcing and insulating insert 53 in the manner of a serving dish illustrated in FIG. 1. The plastic insert 53 while snugly fitting Within the insulating chamber 52 will not completely fill the chamber but it is of a size and shape to make allowances for linear expansion of the insert. Thus, the insert not only serves to reinforce the double wall container as in the serving dish illustrated in FIG. 1, but also serves to increase the insulating effect of the container.

It is also pointed out that the inner surface of the outer shell may be provided with a reflective metallic coating 54 of similar nature to the coating of the outer shell in the serving dish illustrated in FIG. 1. Again, it is pointed out that this metallic coating serves not only to increase the insulating eificiency of the tumbler but also imparts a highly ornamental appearance to the receptacle.

It will be noted that the bottom wall 47 of the inner shell 40 has a thin annular shaped portion 47a and a thickened central portion 47 b, the latter having a depending centering valve element 470. Thus, it will be seen that the inner shell 49 illustrated in FIG. 2 differs somewhat from the inner shell illustrated in FIG. 1 since the inner shell in FIG. 1 was constructed of substantially uniform thickness while the bottom Wall 47 of the shell 45 has a thin annular portion. It will be noted that the thickened circular centrally located portion 47b is positioned in fluid sealing abutting relation with respect to the valve seat 46b of the 'outlet 46. When so seated, the depending valve centering element 470 projects into the outlet 46a of the lower wall 46. 7

When the tumbler illustrated in FIG. 2 is subjected to elevated temperatures as by pouring a hot beverage therein or when the tumbler is immersed in hot waters associated with conventional household automatic dishwashing machines, the temperature of the gas trapped within the insulating chamber 52 will be elevated. When so elevated, the gases therein will expand and exert increased pressure 'against the inner and outer shells in accordance with Charles law in the manner of the embodiment illustrated in FIG. 1. However, because of the thin annular portion 47:: of the bottom wall of the inner shell 40, this thin portion will react to the increased pressure and will be moved away from the opposed bottom Wall portion 42 of the outer shell 41. Thus, movement of the bottom wall 47 away from the bottom wall 42 causes corresponding movement of the valve element 47b relative to the valve seat 46b. When the thickened valve element 47 b is moved out of engagement with respect to the valve seat 4617, then the insulating chamber 52 is in communicating relation with the exterior of the excessive gas pressures will be relieved since venting of the double wall container becomes automatic.

It should be pointed out that the valve element 47b u is preloaded with respect to its seated relation with the valve seat 46b and the preload force may be accomplished by molding the bottom wall 47 of substantially planar configuration so that this bottom Wall, as illustrated in FIG. 2 will be slightly deformed upwardly when the inner and outer shells are assembled.

The thinned out portion 47a of the inner shell 40 also causes the bottom wall to function in the manner of a diaphragm type self sealing valve since the bottom portion will initially react to changes in gas pressure within the in ulating chamber 52. Because the bottom wall 47 of the tumbler has a relatively small surface area as compared to the peripheral walls of the inner shell 40,

it is therefore preferred to thin out the portion of this bottom wall to permit ready movement of this bottom wall in response to the increase in air pressure within the insulating chamber 52. It will be noted as in FIG. 1, that the snap coupling fitting permits different kinds of plastics to be used and the self venting feature in both embodiments also permits the cheaper grade low heat resistant type plastics to be used in the manufacture of these double wall containers. It will be pointed out that even though the inner and outer shells are subjected to temperatures which tend to cause the plastic comprising the shells to be somewhat softened, these shells will not deform since there will be no pressure exerted internally or externally by expanding gases. The self venting feature as well as the self scaling function of my novel container lends itself to the use of the cheaper low heat resistant type plastic thus permitting the wide variety of plastic materials to be now used in the manufacture of these double wall type insulating containers.

From the foregoing, it will be seen that I have provided a novel double wall structure preferably of the insulating receptacle or container type which incorporates therein a self-venting and self-scaling feature so that deformation attributable to internal gas pressures exerted against softened heated plastics are greatly minimized if not precluded.

it will also be noted that because of the unique con struction of my novel self-venting, double Wall receptacle,

that as the molding of the diaphragm valve mechanism into the inner and outer shells, that the receptacles may be produced without an increase in cost.

it will also be noted that opposed wall portions ofthe container shells function as a diaphragm valve wherein the internal and external pressure effected is utilized to accomplish a self-venting result.

It will, therefore, be seen that we have provided a novel and improved double wall heat insulating type receptacle formed of plastic material which is not only of simple and inexpensive construction but one which functions in a moreefiicient manner than any heretofore known comparable device.

it will, of course, be understood that various changes may be made in the form, details, arrangement and roportion of the various parts without departing from the general scope of my invention.

What is claimed is: v

1. Self venting double wml stru ture comprising a pair of walls disposed in opposed spaced apart relationship and each being constructed of a resilient plastic material and being joined with sealed effect to define an insulating gas chamber the-rebetween, one of said Walls having an outlet therein interconnecting said insulating chamber in communicating relation with the exterior, valve means on said walls normally closing said outlet and being movable between outlet opening and closed positions upon relative shifting of said Walls towards and away from each other in response to changes of gas pressure in said insulating chamber whereby the gas pressure. within the insulating chamber will be automatically reduced to thereby preclude deformation of said walls.

2. A selfwenting plastic receptacle for use in holding and serving foods, beverages, ice and the like comp-rising a pair of generally symmetrical inner and outer shells of hard plastic material, means for joining said shells in sealed effect to provide insulating chamber in communieating relation with the exterior, and valve means on said Walls normally closing said outlet and being movable between outlet opening and closed position upon relative shifting of said walls towards and away from each other in response to changes of the gas pressure in said insulating chamber.

3. A self-venting double wall and plastic receptacle r-"r use in holding and serving foods, beverages, ice and the like comprising a pair of generally symmetrical inner and outer shells of relatively hard plastic material, means for joining said shells with seal effect to provide an insulating chamber therebetween, one of said shells having an outlet therein interconnecting said insulating chamber in communicating relation with the exterior, the other or" said shells having a valve element for normally closing said outlet, the latter being readily opened upon relative shitting or" said shells in response to changes of gas pressure in said insulating chamber whereby the gas pressure within the insulating chamber Will be automaticflly relieved to thereby preclude deformation of said shells.

4. A self-venting double wall receptacle for use in holding and serving foods, beverages, ice and the like comprising a pair of generally symmetrical inner and outer shells of relatively hard plastic material, means for joining said shells with seal eilect to provide an insulating chamber tlrerebetween, one oi said shells having an outlet therein interconnecting said insulating chamber in communicating relation with the exterior, the outer of said shells having a valve element for normally closing said outlet, the latter be ng readily opened upon relative shifting of said shells in response to changes of gas pressure in said insulatin chamber whereby the gas pressure within the insulating chamber will be automatically relieved to thereby preclude deformation of said shells.

5. A self-venting double Wall receptacle for use in holding and serving foods, beverages, ice and the like comprising a pair of generally symmetrical inner and outer shells of hard plastic material, means for joining said shells in sealed effect to provide an insulating chantber therebetween, one of said shells having an outlet therein interconnecting said insulating chamber in cornmunicating relation with the exterior, the other of said shells having a valve element for normally closing said outlet and being movable between outlet opening and closed positions upon shifting of said other shell towards and away from said one shell in response to changes of gas pressure in said insulating chamber whereby the gas pressure within the insulating chamber will be automatically relieved to thereby preclude deformation of lalls.

6. A high etficiency double wall self-venting receptacle for use in holding and serving foods, beverages and the like coniprisn a pair of generally symmetrical inner and outer shells of hard plastic, snap coupling means for joining the peripheral edge portions of said shells with sefled effect to define an insulating chamber therebetween said snap coupling means including an annular shaped male snap coupling element formed adjacent the peripheral edge portion of one of s shells, and a recess formed in the peripheral edge portion of the other of said shells for receiving the male snap coupling element in sealed relation therein, an outlet in one of said shells inter-connecting said insulating chamber in communication with the exterior, a valve element on the other of said shells for normally enclosin said outlet and being movable between outlet opening and closed positions upon shifting of said other shells towards and away from said one shell in esponse to changes of gas pressure in said insulating chznnber whereby the gas pressure within the insulating chamber will be automatically reduced to thereby preclude deformation of said Walls.

7. Self-venting double wall receptacle for use in holding and serving foods, beverages, ice and the like comprising a pair of generally symm ical inner and outer shells of plastic material, means ior joinin shells in sealed effect to provide an insulating chamber therebetween, said outer shell having an outlet therein interconnecting said insulating chamber in communicating relation with the exterior, said inner shell having a valve element integrally formed therewith for normally closing said outlet and being movable between outlet opening and closed positions upon shifting of said inner shell from said outer shell in response to changes of gas pressure in said insulating chamber whereby excessive gas pressure within the insulating chamber will he automatically relieved to preclude deformation of said shells.

References Cl-ed in the file of this patent UNITED STATES PATENTS 722,688 Levy Jan. 4, 1932 

1. SELF VENTING DOUBLE WALL STRUCTURE COMPRISING A PAIR OF WALLS DISPOSED IN OPPOSED SPACED APART RELATIONSHIP AND EACH BEING CONSTRUCTED OF A RESILIENT PLASTIC MATERIAL AND BEING JOINED WITH SEALED EFFECT TO DEFINE AN INSULATING GAS CHAMBER THEREBETWEEN, ONE OF SAID WALLS HAVING AN OUTLET THEREIN INTERCONNECTING SAID INSULATING CHAMBER IN COMMUNICATING RELATION WITH THE EXTERIOR, VALVE MEANS ON SAID WALLS NORMALLY CLOSING SAID OUTLET AND BEING MOVABLE BETWEEN OUTLET OPENING AND CLOSED POSITIONS UPON RELATIVE SHIFTING OF SAID WALLS TOWARDS AND AWAY FROM EACH OTHER IN RESPONSE TO CHANGES OF GAS PRESSURE IN SAID INSULATING CHAMBER WHEREBY THE GAS PRESSURE WITHIN THE INSULATING CHAMBER WILL BE AUTOMATICALLY REDUCED TO THEREBY PRECLUDE DEFORMATION OF SAID WALLS. 